1. Field of the Invention
This invention pertains to a coated abrasive article having an electrically conductive material incorporated into the backing thereof; and a method of making the same. The abrasive article is useful in reducing the accumulation of the static electric charge in the abrasive article during abrading of a workpiece.
2. Description of the Related Art
Coated abrasives, considered the premier tool for abrading and finishing wood and wood-like materials, unfortunately suffer fron the generation of static electricity during their use. Static electricity generated by the constant separation of the abrasive product from the workpiece, the machinery drive rolls, idler rolls, and support pad for the abrasive product. This static charge is typically on the order of 50 to 100 kilovolts.
Static electricity is responsible for numerous problems. For example, a sudden discharge of the accumulated static charge can cause injury to an operator in the form of an electric shock or it can cause the ignition of wood dust particles, which poses a serious threat of fire or explosion. The static charge also causes the sawdust to cling to various surfaces, including that of the coated abrasive, the abrading machine and the electrically insulating wood workpiece, thereby making it difficult to remove by use of a conventional exhaust system. If the static electrical charge is reduced or eliminated, the coated abrasive article can have a significantly longer useful life and the potential for the above-mentioned hazards can be eliminated or reduced.
Many attempts, with varying degree of success, have been made to solve the static electricity problem. One common approach has been to incorporate an electrically conductive or antistatic material into the coated abrasive construction to eliminate the accumulation of electrical charge. For example, U.S. Pat. No. 3,163,968 (Nafus) discloses a coated abrasive article having a coating comprising graphite in the binder on the surface opposite the abrasive material. U.S. Pat. No. 3,168,387 (Adams) discloses a coated abrasive having a metal leaf pigment over the abrasive grains. U.S. Pat. No. 3,377,264 (Duke) discloses an electrically conductive layer, such as a metal foil, overlying the front surface of a coated abrasive.
U.S. Pat. No. 3,942,959 (Markoo et al.) teaches a coated abrasive construction having an electrically conductive resin layer sandwiched between two electrically nonconductive resin layers to prevent the accumulation of electrostatic charge during grinding. In the latter construction, the resin layer is made electrically conductive by incorporating into the resin an electrically conductive filler which may be a metal alloy, metal pigment, metal salt, or metal complex.
U.S. Pat. No. 3,992,178 (Markoo et al.) discloses a coated abrasive article having an outer layer comprised of graphite particles in a bonding resin which reduces the electrostatic charges generated during grinding.
U.S. Pat. No. 4,826,508 (Schwartz et al.) discloses a flexible abrasive member comprising a length of flexible fabric that has been treated to render it electrically conductive, an electrically non-conductive mesh layer applied to one surface of the fabric, said non-conductive mesh layer having a multitude of discrete openings therein, and electrodeposited metal adhering to the electrically conductive fabric in each of the openings, the electrodeposited metal having particulate abrasive material embedded therein.
U.S. Pat. No. 5,061,294 (Harmer et al.) teaches a coated abrasive that is rendered conductive by the addition of a doped conjugated polymer.